There are numerous components in industrial and utility installations which require on-site, pre-service inspection and/or periodic in-service inspection to verify continued serviceability. Such inspection frequently includes dimensional measurements. A notable example is the on-site inspection of components of a nuclear reactor, especially replaceable components such as control rods, fuel elements and fuel channels.
For example, a typical fuel assembly having a removable and reusable flow channel is shown in U.S. Pat. No. 3,689,358. Such an elongated square tubular fuel channel may be in the order of 13 cm in transverse cross section dimensions and in the order of 4 m in length. It is necessary to assure that the four major surfaces of such channels are sufficiently flat so as not to interfere with the insertion of control rods between fuel assemblies during operation in the nuclear reactor core. Dimensional tolerances over the length of such a channel may be in the order of 0.127 mm. To perform the necessary flatness measurement of such a component, an elongated accurate and stable measuring fixture is required.
Since flow channels, and other reactor components, which have been subjected to reactor service are radioactive, it is necessary that the measuring device be remotely operable under water to protect the equipment operators from radiation. It is desirable that the measuring device be sufficiently portable for repositioning within a water pool, for movement from one pool to another, and for removal to dry storage when not in use.
Thus an object of the invention is a portable device or fixture for accurate dimensional measurement of radioactive components.